Interaction Enhanced Imaging of Individual Rydberg Atoms in Dense Gases

We propose a new all-optical method to image individual Rydberg atoms embedded within dense gases of ground state atoms. The scheme exploits interaction-induced shifts on highly polarizable excited states of probe atoms, which can be spatially resolved via an electromagnetically induced transparency resonance. Using a realistic model, we show that it is possible to image individual Rydberg atoms with enhanced sensitivity and high resolution despite photon-shot noise and atomic density fluctuations. This new imaging scheme could be extended to other impurities such as ions, and is ideally suited to equilibrium and dynamical studies of complex many-body phenomena involving strongly interacting particles. As an example we study blockade effects and correlations in the distribution of Rydberg atoms optically excited from a dense gas.

Figure 1

Scheme for imaging individual impurities within a dense atomic gas. Impurity particles (crosses) are embedded within a dense two-dimensional atomic gas of probe atoms. The probe atoms interact with two light fields (coupling and probe) via a two-photon resonance with an excited state $|r⟩$. This produces an EIT resonance on the lower transition. However, strong interactions with an impurity lead to a frequency shift $U$ of the resonance within a critical radius $R_c$. The change in absorption properties of many surrounding atoms makes it possible to map the distribution of impurities to the absorption profile of a probe laser for analysis.

Figure 2

Imaginary part of the susceptibility. (a) $\mathrm{Im}[\chi ]$ as a function of probe detuning for ${\Omega }_c=1$, ${\Gamma }_c=0.05$, and ${\Delta }_c=0$ (in units of ${\Gamma }_p$) for various distances from the Rydberg atom. The solid line is for $d\to \infty$, the dashed line corresponds to $d=R_c$, and the dotted line is for $d=R_c/2$. (b) $\mathrm{Im}[\chi ]$ as a function of distance from the Rydberg atom with ${\Delta }_p=0$.

Figure 3

Simulated absorption images of atom distributions including photon-shot noise and atomic density fluctuations. In (a), without the coupling beam, a regular absorption image of the probe atoms is obtained. The color code indicates absorption. With the coupling on (b) the probe atoms are rendered transparent, except for those in the vicinity of a Rydberg atom. Parameters of the simulation can be found in the text.

Figure 4

Pair distribution and angular correlation function of 15 simulated Rydberg images. The solid black line shows $g(r)-1$ computed from the absorption images for 15 realizations. The shaded bars show $g(r)-1$ taken directly from the simulated Rydberg atom coordinates with a bin size of $0.5\mu \mathrm{m}$. The clear shell structure which reflects translational order between nearest and next-nearest neighbors is preserved by the images. The inset shows the angular correlation function for the radius of the first shell.